Plant Pathology - Study Mode
[#596] The law of limiting factors for photoshythesis was enunciated by
Correct Answer
(D) Blackman
Explanation
Solution: The law of limiting factors for photosynthesis was enunciated by Blackman. In 1905 Frederick Blackman articulated the role of limiting factors as follows: "When a process is conditioned as to its rapidity by several separate factors the rate of the process is limited by the pace of the slowest factor." The identification of a factor as limiting is possible only in distinction to one or more other factors that are non-limiting.
[#597] Which one of the following is a single cell fungi
Correct Answer
(A) Yeast
Explanation
Solution: Yeast is a single cell fungus. Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. Yeasts are unicellular organisms with some species having the ability to develop multicellular characteristics by forming strings of connected budding cells known as pseudo hyphae or false hyphae. Yeast sizes vary greatly, depending on species and environment, typically measuring 3 - 4 µm in diameter, although some yeasts can grow to 40 µm in size.
[#598] Outer wall of pollen grain is formed of
Correct Answer
(D) Sporopollenin
Explanation
Solution: Outer wall of pollen grain is formed of Sporopollenin. Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of gymnosperms. Each pollen grain contains vegetative cells and a generative (reproductive) cell. In flowering plants the vegetative tube cell produces the pollen tube, and the generative cell divides to form the two sperm nuclei.
[#599] Polar nuclei are located in
Correct Answer
(B) Embryo sac
Explanation
Solution: Polar nuclei are located in the Embryo sac. The female gametophyte is also commonly called the embryo sac or megagametophyte. The female gametophyte develops within the ovule and generally consists of three antipodal cells, one central cell, two synergid cells, and one egg cell. Central cell is formed by the fusion of two polar nuclei. Out of two, one is derived from the micropylar end and the other from the chalazal end.
[#600] Club root of crucifers can be controlled by application of
Correct Answer
(B) Lime
Explanation
Solution: Club root of crucifers can be controlled by the application of Lime. Clubroot is a fungal disease that affects several plants in the cabbage family including cabbages, radishes, mustard and ornamentals such as candytuft. It is caused by the fungus Plasmodiophora brassicae and gets its name from the club-like roots it induces in infected plants. Since problems are more severe in acid soils (pH 5.0 - 7.0) adding lime to acid soils can help control the disease.